In wireless communications networks, a frame structure for long term evolution (“LTE”) frequency division duplex (“FDD”) may be used. Alternatively, a frame structure for time division duplex (“FDD”) may be used. A radio frame of 10 milliseconds (“ms”) may include 10 subframes, each of which is 1 ms. Each subframe further may include two slots, each of which is 0.5 ms. Within each slot, a number of orthogonal frequency-division multiplexing (“OFDM”) symbols may be transmitted. The transmitted signal in each slot on an antenna port may be described by a resource grid comprising NRBDLNscRB subcarriers and NsymbDL OFDM symbols, where NRBDL is a number of resource blocks (“RBs”) in the downlink (“DL”) (which is dependent on the transmission bandwidth of a cell); NscRB is the number of subcarriers in each RB; and each subcarrier occupies a certain frequency of size Δf. The values of NscRB, Δf, and NsymbDL may depend on a cyclic prefix as shown in Table 1.
TABLE 1ConfigurationNscRBNsymbDLNormal Cyclic PrefixΔf = 15 kHz127Extended Cyclic PrefixΔf = 15 kHz6Δf = 7.5 kHz243
In certain configurations, an antenna port may refer to a logical antenna port (i.e., it may not necessarily refer to a physical antenna or antenna element). Mapping between an antenna port and physical antenna element(s) may be implementation specific. In other words, different devices may have a different mapping of physical antenna element(s) to the same antenna port. A receiving device may assume that the signals transmitted on the same antenna port go through the same channel. Moreover, a receiving device cannot assume signals transmitted on different antenna ports go through the same channel.
In certain wireless communication networks, the transmission time interval (“TTI”) may be 1 ms. In other wireless communication networks, such as networks using shortened TTIs (“s-TTIs”), the s-TTI may be less than 1 ms. In such wireless communication networks, semi-persistent scheduling (“SPS”) may be used. In some wireless communication networks, scheduling conflicts may occur.